We are very grateful to Dr. J. Harju for his contribution to this work, to Dr. Lars E.B. Johansson for the help with the observations in Onsala, to the SEST staff, to Alexander Lapinov for calculating HNCO line strengths and to the referee, Dr. C.M. Walmsley, for the very useful detailed comments. I.Z. thanks the Helsinki University Observatory and Max-Planck-Institut für Radioastronomie for the hospitality. He was also supported in part by the DFG grant 436 RUS 113/203/0, INTAS grant 93-2168-ext, NASA grant provided via CRDF RP0-841 and grants 96-02-16472, 99-02-16556 from the Russian Foundation for Basic Research. This research has made use of the Simbad database, operated at CDS, Strasbourg, France.
© European Southern Observatory (ESO) 2000
Online publication: October 10, 2000